add typehints and return types

src/Provider/Node/FallbackNodeProvider.php

@@ -38,7 +38,7 @@ class FallbackNodeProvider implements NodeProviderInterface
     /**
      * @inheritDoc
      */
-    public function getNode()
+    public function getNode(): ?string
     {
         foreach ($this->nodeProviders as $provider) {
             if ($node = $provider->getNode()) {

src/Provider/Node/RandomNodeProvider.php

@@ -27,7 +27,7 @@ class RandomNodeProvider implements NodeProviderInterface
     /**
      * @inheritDoc
      */
-    public function getNode()
+    public function getNode(): string
     {
         try {
             $nodeBytes = random_bytes(6);

src/Uuid.php

@@ -569,6 +569,9 @@ class Uuid implements UuidInterface
         return (int) hexdec($this->getTimestampHex());
     }
 
+    /**
+     * @inheritdoc
+     */
     public function getTimestampHex(): string
     {
         if ($this->getVersion() !== 1) {